Radio receiving system



Aug 20, I929. s. CABOT RADIO RECEIVING SYSTEM 5 Sheets-Sheet Filed Aug. 26, 1924 OOOOIIOO Aug. 20, 1929. s, ABQT 1,725,615

RADIO RECEIVING SYSTEM Filed Aug. 26, 1924 5 Sheets-Sheet 2 Aug. 20, 1929. s CABOT 1,725,615

RADIO RECEIVING SYSTEM Filed Aug. 26. 1924 5 Sheets-Sheet 5 Aug. 20, 1929. s. CABOT 1,725,615

RADIO RECEIVING SYSTEM Filed Aug. 26. 1924 5 Sheets-Sheet 5 SheetsSheet Filed Aug. 26, 1924 FIJI.

Patented Aug. 20, 1929.

UNITED STATES SEWALL CABOT, or BROOKLINE, MASSACHUSETTS.

RADIO RECEIVING SYSTEM.

Application filed August 26, 1924. Serial No. 734,205.

This invention, which is an improvement on the system described in my application Serial No. 563,611, filed May 25, 1922, issued July 14., 1925, as Patent No. 1,545,940, re-

lates to radio-receiving systems of the radiofrequency amplifier type in which a threeelectrode vacuum tube is interposed between an oscillatory receiving circuit and a second oscillatory circuit, the said circuits not being exteriorly coupled 0r interlinked, but

coupled or interlinked only by the capacity between the elements of said tube.

In systems of this type if capacity only is used to tune both circuits, regeneration is very much stronger on short wave lengths,

and if inductance only is varied, regeneration is much stronger on long wave lengths.

I have discovered that if the inductance of one circuit is kept constant and the capacity thereof only is varied, and the capacity of the other circuit is kept constant or approximately constant, and the inductance thereof only is varied, the regeneration will be of substantially equal intensity for all wave lengths within the range of the system.

It is therefore the principal object of my invention to provide a radio-receiving system of the radio-frequency amplifier type in which regeneration of substantially the same intensity will be obtained for all wave lengths within the range of the system, and

this object I accomplish, in the present instance, by mechanically connecting the variable condenser of the input circuit of the vacuum tube with the variable inductance of the output circuit thereof, in such manner that for every position of the movable con necting means, such as a shaft, the product of inductance by capacity in the input circuit of the tube is equal to the product of inductance by capacity in the output circuit thereof.

A further object of my invention is to provide a method of controlling the oscillatory phenomena in an electromagnetic-receiving system of the radio-frequency amplifier type by simultaneously varying the capacity of the input circuit and the inductance of the output circuit of a vacuum tube while maintaining constant the inductance of said input circuit and the capacity of said output circuit.

In the drawings which accompany and form a part of this specification Fig. 1 is a diagram of a radio-receiving system embodying my invention;

Fig. 2 is a diagram of the stator of my improved D-transformer variometer, the winding of the-rotor thereof being identical with that of said stator; I

Fig. 3 is a side elevation of one form of apparatus embodying my invention;

Fig. 4 is a plan view of the D-transformer variometer shown in Fig. 3;

Fig. 5 is a plan View of the rotor of said variometer Fig. 6 is a plan view of the stator of said variolneter;

Fig. 7 is a section taken on the line 7-7 of Fig. 4;;

In the particular drawings selected for more fully disclosing the principle of my invention, and which are to be taken as illustrative rather than restrictive, inasmuch as my invention may be embodied in a Variety of apparatus and circuit arrangements, L is an antenna herein shown as a loop con sisting of a plurality of turns, the terminals of said loop being connected across the variable condenser C,, so that said loop and condenser form a parallel-branch circuit having inductance in one branch and capactiy in the other.

It will be understood however that I may employ an antenna of any suitable type coupled in any appropriate manner with the input circuit of the audion, or to a closed receiving circuit connected with said input circuit. The output circuit of said audion A is connected at the points a, b, to the primaries P, P, P, P which are very closely coupled to the secondaries S, S, S, S across which the fixed condenser 0 is connected, said secondaries and said condenser constituting a parallel branch circuit having variable inductance in one branch and fixed capacity'in the other. A vernier condenser 6,, preferably is used in conjunction with said condenser 0 The input circuit of the detector audion A is connected at the points 0, d, to the parallel-branch circuit S, S, S", S, C and the output circuit thereof includes the signal-indicating device T, such as a high'resistance telephone, or as will be obvious, the audion A may be onerof a series of amplifying tubes. Batteries B B are connected in the plate circuits of the audions A A respectively, and the filaments thereof are heated by the battery B.

The variable condenser 0 and the variable inductance P, P, P, P, S, S, S",

S, are mounted on the rod R, rotatable by the knob K, which rod constitutes a movable means mechanically connecting these elements so that said condenser and inductance may be simultaneously varied, the values of the several electromagnetic constants being so chosen that for every angular position of said rod, the product of the inductance of. the parallel-branch circuit L C, by the capacity thereof will be equal to the product ot the inductance of the-parallel-branch circuit S, S,;S, S, C, by the capacity of the latter circuit.

The variable inductance of the parallelbranch circuit S, S, S, S, C, may be a variometer, such as shown in my Patent No. 1,545,940, of any suitable type, such for example as a D-variometer, or it may be a variometer-transtormer, such for example as a Dvariometer-transformer, such as indicated conventionally in Figs. 1 and 2, and illustrated in detail in the other figures. In

the case of the DVariometer-transformer herein shown and described, the coupling between the primaries and secondaries is so tight that the several coils constitute the inductance element of a parallel-branch circuit, of which the capacity element is the condenser C,.

Each primary P, P, P, P, of the D- transformer-variometer consists of a relatively small number of turns, such for example, as eighteen turns, and each secondary S, S, S", S, consists of a relatively larger number of turns, .for instance, fortyeight turns oi wire somewhat larger than that used to wind the primaries.

In the present instance the windings are of the pancake type and are mounted on insulating plates 1, 2. The outside terminal P0 of the primary'P is connected by the conductor 3 to the outside terminal Po of the primary P, and the inside terminal Pi of said primary P is connected by the conductor at to the inside terminal Pz' of the primary P, in the case of the stator, which is mounted on the plate 1. In like manner the outside terminal S0 of the secondary S of the stator is connected by the conductor 5 to the outside terminal So of the second ary S, while the insideterminal Si of the secondary S is connected by the conductor 6 tosthe inside terminal Si of the secondary The outside terminals P"0, P0 of the rotor primaries P, .P are connected together by the conductor 7 as shown in Fig. 1, and the inside terminals Pz', P',i are connected together by the conductors. The

outside terminals S0, So of the rotor secondaries S", S, are connected together by the conductor 9, and the inside terminals Sz', S 6 of said secondaries are connected togetherby the conductor 10.

The outside terminals of the four primaries are connected by the conductor 11 to the positiveterminal of the battery B by way of the point I). The inside terminals of said primaries are connected by the conductor 12 to the plate Pl, of the audion A, by way of the point a.

In like manner the outside terminals of the four secondaries are connected to the negativepole of the battery B and the condenser C through conductor 13 by way of the point (Z, and the inside terminals of said secondaries are connected to the grid G, of the audion A and the condenser C through the conductor 14: by way of the point 0.

Preferably the line wire primary wind ings are wound directly in with the turns forming the outside of the coil, as indicated in Fig. 2.

When the primaries and secondaries are arranged and connected in the manner shown in Figs. 1 and 2, all electrostatic coupling between primary and secondary is eliminated, because no potential difference can ever exist between any portion of the primary turns and the secondary turns which are adjacent thereto.

As is well understood, the inductance element of the parallel-branch circuit has a minimum value when the rotor and stator are so related angularly that the windings of the one are respectively in the opposite direction to those of the other, and the inductance thereof has its maximum value when the stator is rotated 180 from its initial position.

The operation is as follows: By means of the knob or knurled head K the rod R, on which are mounted the movable plates of the condenser C, and the rotor of the D- transt'ormervariometer, is turned to tune in the station which is desired to be received,

and the final adjustments, ii": necessary, may.

be made by the Vernier C the capacity of the condenser 0 and the inductance of the loop L remaining fixed. The electromagnetic constants are so adjusted by means now well understood to those skilled in the art, that for every position of the knob, K, the input and output circuits of the tube A,, will be attuned to the same frequency, and inasmuch as the capacity only of the input circuit and the inductance only of the output circuit are varied, regeneration will be of substantially the same intensity tor all frequencies within the range of the system.

While it will be readily understood by those skilled in the art that the principle of. my invention may be embodied in a variety of forms, I shall now describe in detail one arrangement of apparatus which has given good results in practice.

A plate 1 of bakelite or other suitable insulating material carries on its inner face the stator windings P, S, P, S, and the juxtaposed face of the insulating plate 2 carries the rotor windings P, S, P, S', the said plate 2 being mounted on the shaft, R and secured thereto by the set-screw 15, and the rotating plate 16 of the condenser C, also being mounted on said shaft, so that by rotating said shaft by the knob or head K (Fig. 1) attached to the projecting end of said shaft, the capacity of the input circuit of the tube A, and the inductance of the output circuit thereof may be varied in the manner hereinbefore set forth.

By means of the head 17 and friction drive 18, 19 a micrometer variation in the capacity of said condenser may be obtained.

A spider 20 shown in the present instance as having four arms, is mounted by the studs 21 on the plate 1, and the hub 22 of the condenser frame is secured by the setscrew 23 to the sleeve 24 cast integral with the arms 20. Secured to the rotor plate 1 is a hub 25 carrying an insulation sleeve 26 which supports spaced insulation washers forming grooves 27 for receiving the flexible conductors 7, 8, 9 and 10, above mentioned in connection with Fig. 1, said conductors serving to connect the primaries and. secondaries, respectively, of the rotor in parallel. The several terminals of the rotor windings disposed as aforesaid on the outer face of the plate 2, are brought through to the inner face of said plate and connected to conducting strips 28 disposed in circumferential grooves in the bushing 26, and the ends of which terminate respectively at the points 29 in the several grooves 27, and at said points 29 the several flexible conduc tors 7, 8,9 and 10 are soldered to said strips. The other ends of the flexible conductors are connected to clips 30 secured to insulation blocks 31 which are supported by the arms 20, as indicated in Fig. 4, and the several clips 30 are connected by bus-bars 7, 8', 9', 10' to binding-posts a, b, 0, (Z, respectively, (Figs. 3 and 1), the said bind ing-posts being indicated in Fig. 1.

Stator windings are connected in the manner above set forth in connection with Fig. 1 by conductors 3, 4t, 5, 6 which are disposed on the outer face of said plate, as indicated in Fig. 6.

Having thus described an illustrative embod ment of my invention Without however limiting the same thereto, what I claim and desire to secure by Letters Patent is 1. In a radio-receiving system, a three-electrode vacuum tube, a tuning element in the input circuit of said vacuum tube, and a variable inductance in the output circuit of said vacuum tube, said variable inductance comprising a primary winding, a secondary said second vacuum tube with said secondaries.

2. In a radio-receiving system, a threeelectrode vacuum tube, a tuning elementin the input circuit of said vacuum tube, and a variable inductance in the output circuit of said vacuum tube, said variable inductance comprising a primary winding, a secondary winding inductively related thereto, a second primary winding, and a secondary winding inductively related to said second primary winding, said primary and secondary windings being relatively movable with respect to said second primary and second secondary, means connecting said primaries in parallel, means connecting said secondaries in parallel, a fixed condenser connected in parallel with said variable inductance, a second three-electrode vacuum tube, and means connecting the input circuit of said second vacuum tube with said secondaries.

3. In a radio-receiving system, a threeelectrode vacuum tube, a tuning element in the input circuit of said vacuum tube and a variable inductance in the output circuit of said vacuum tube, said variable inductance comprising a stator winding and a rotor winding, said stator winding comprising two primaries connected in parallel, and two secondaries, each inductively related to one of said primaries and connected in parallel, and said rotor winding comprising two primaries connected in parallel and twosecondaries, each inductively related to one of said primaries and connected in parallel, means connecting the stator and rotor primaries in parallel, means connecting the stator and rotor secondaries in parallel, a fixed condenser connected in parallel with said secondaries, a second three-electrode vacuum tube, and means connecting the input circuit of said second vacuum tube with said secondaries.

In testimony whereof, I have hereunto subscribed my name this 21 day of August, 1924:.

SEWALL OABOT. 

